PEPTIDE INHIBITORS OF MITOGENESIS AND MOTOGENESIS

Abstract: The invention in the field of cell biology relates to novel peptides able to interact with intracellular signal transducers, thus interfering with signal transduction pathways leading to cell proliferation and motility. The peptides of the invention may be chemically synthesized from single amino acids and/or preformed peptides of two or more amino acid residues. The peptides of the invention find a useful application in the treatment of a neoplastic disease.

Description: TITLE: PEPTIDE INHIBITORS OF MITOGENESIS AND MOTOGENESIS Field of the invention The invention in the field of cell biology relates to novel peptides able to interact with intracellular signal transducers, thus interfering with signal transduction pathways leading to cell proliferation and motility. Description of the background art Polypeptide growth factors mediate their physiological responses by binding cell surface receptors with tyrosine kinase enzymatic activity (reviewed in Ullrich, A. and Schlessinger, J. , Cell 61: 203-211 (1990)). Upon binding of these ligands, growth factor receptors undergo dimerization followed by the autophosphorylation of specific tyrosine residues. Among the intracellular milieu of proteins are molecules with defined biological functions that serve as substrates for ligand-activated tyrosine kinase receptors. The experimental evidences accumulated in the last few years indicate that, upon binding to the receptor, these substrate molecules switch into an activated form and become part of the critical signaling pathway used by growth factors to control cell proliferation. A number of the cytoplasmic molecules that mediate cellular response to growth factors have been shown to interact with activated receptors through their SRC homology region 2 (SH2) domain (Koch, C . , et al., Science 252 : 668-674 (1991) ) . The SH2 domain is a conserved protein module of approximately 100 aminoacids which is found in a remarkably diverse group of cytoplasmic signaling proteins. Proteins with SH2 domains frequently possess another distinct sequence of about 50 residues, the SH3 domain, which is also implicated in the regulation of protein- protein interactions during signal transduction (see Clark, S.G., et al., Nature 356: 340-344 (1992) and references therein) . Receptor autophosphorylation following ligand binding acts as a molecular switch to create binding sites for the SH2 domain of the cytoplasmic signaling proteins (Anderson, D., et al., Science 250: 979-982 (1990)), which thereby become targets for activation. SH2 domains directly recognize phosphotyrosine (Matsuda, M. , et al., Science 241 1537-1539 (1990)). However, high affinity binding of an SH2 domain requires that the phosphotyrosine be embedded within a specific amino acid sequence, as originally suggested by an examination of SH2-binding sites (Cantley, L.C., et al., Cell 64 . : 281-302 (1991)). For example, the SH2-containing proteins phosphatidylinositol (PI) 3-kinase, the Ras GTP-ase- activating protein (Ras GAP) and phospholipase C-γ (PLC-7) each bind to different autophosphorylation sites of the receptor for platelet-derived growth factor (Kashishian, A. , et al., EMBO J. .11: 1373-1382 (1992); Fantl, .J. , et al., Cell 69.: 413-423 (1992)). Autophosphorylation sites acting as specific docking sites for PI 3-kinase, PLC-γ and Ras GAP, have been identified also in epidermal growth factor receptor (EGF-R) , colony- stimulating factor 1 receptor (CSF-IR) and fibroblast growth factor receptor (FGF-R) (Cantley, L.C., et al., Cell 64: 281-302 (1991); Mohammadi, M. , et al., Mol. Cell. Biol. .11: 5068-5078 (1991); Reedijk, M. , et al. , EMBO J. .41: 1365-1372 (1992); Rotin, D. , et al. , EMBO J. 11: 559-567 (1992)). It has been demonstrated that relatively short peptide sequences corresponding to PDGF receptor phosphorylation sites inhibited the interaction between the activated PDGF receptor and PI 3-kinase (Escobedo, J.A. , et al., Mol. Cell. Biol. 11: 1125-1132). The residues immediately C-terminal to the phosphotyrosine, especially those at the +1, +2 and +3 positions, appear to provide selectivity for specific SH2 domains. Thus, a recognition motif for the p85 submit of PI 3-kinase has been identified in the PDGF receptor: the sequence is Tyr-Met/Val-Xxx-Met (YMXM or YVXM) wherein Xxx and X represent any amino acid residue in the three-letter or one- letter code respectively (Domchek, S.M., et al., Biochemistry 31: 9865-9870 (1992)). The identification of new members of the SH2-containing molecules family as well as of the respective recognition motif is rapidly proceeding. A direct involvement of some of these molecules in eliciting the biological response to a ligand has been demonstrated. This is the case for the protein Grb2 which associates, through its SH2 domain, to both EGF receptor upon ligand stimulation. Microinjection of Grb2 and H-ras protein into mammalian cells resulted in the stimulation of DNA synthesis and hence in a mitogenic effect (Lowenstein E.J., et al., Cell 70: 431-442 (1992)). These results indicate that Grb2 plays a crucial role in the mechanism for growth factor control of ras signaling. While most of the efforts in the last few years have been concentrated on the study of the interaction between cytoplasmic signaling proteins and the best characterized EGF and PDGF receptors, the authors of the present invention have focused their attention on the hepatocyte growth factor (HGF) receptor. HGF, also known as Scatter Factor (SF) , is a heterodimeric protein secreted by cells of mesodermal origin (Stoker, M. , et al.. Nature 327: 239-242 (1987); Weidner, K.M. , et al., J. Cell Biol. HI: 2097-2108 (1990)). The factor induces a spectrum of biological activities in epithelial cells, including mitogenesis, stimulation of cell motility and promotion of matrix invasion (Naka ura, T. , et al., Biochem. Biophys. Res. Comm. 122: 1450-1459 (1984); Stoker, M. et al., Nature 327: 239-242 (1987); Weidner, K.M., et al., J. Cell. Biol. Ill: 2097-2108 (1990); Rubin, J.S. et al., Proc. Natl. Acad. Sci. U.S.A. 8J5: 415-419 (1991)). HGF/SF is also a morphogen in vitro (Stern CD. et al., Development 110: 1271-1284 (1990); Montesano et al. Cell 66: 697-711 (1991)) and a potent angiogenic factor in vitro and in vivo (Bussolino, M.F., et al., J. Cell Biol. 119: 629-641 (1992)) . While the biological effect of HGF/SF varies depending on the target cell, the HGF/SF signal is mediated by a single receptor, the tyrosine kinase encoded by the MET proto- oncogene (for a review see Comoglio, P.M. in I.D. Goldberg and E.M. Rosen (eds) , Hepatocyte Growth Factor - Scatter Factor (HGF/SF) and the C-Met Receptor, Birkhauser Verlag Basel/Switzerland) . The HGF receptor, also known as plθo"^, is a heterodimeric receptor made of an extracellular α and a transmembrane β subunit (Giordano, S. , et al., Nature 339: 155-156 (1989)), both originating from proteolytic cleavage of a common single chain precursor of 170 kDa (Giordano, S., et al., Oncogene ±: 1383-1388 (1989)). NIH3T3 fibroblasts transfected with the human MET cDNA express functional receptors and respond to HGF/SF with increased motility and invasion of extracellular matrices (Giordano S. et al. PNAS, 90: 649-653 (1993)). Uncontrolled tyrosine kinase activity of the HGF/SF receptor has been observed in transformed cell lines, following chromosomal rearrangements (Park et al., Cell 43 : 895-904 (1986)), gene overexpression (Giordano S. et al., Nature 339: 155-186 (1989)), defective post-translational processing (Mondino et al., Mol. Cell. Biol. 11: 6084-6092 (1991)) and autocrine loop. Overexpression of the receptor has been observed in a number of human tumors of epithelial origin (Di Renzo et al., Oncogene 6_: 1997-2003 (1991); Di Renzo et al., Oncogene 2 2549-2553 (1992); Prat et al., Int. J. Cancer .49 . : 323-328 (1991)). This emphasizes the oncogenic potential of the HGF/SF receptor. Little is known about the signal transduction pathways triggered by HGF/SF. The pleiotropic biological response induced by the factor suggests that more than one mechanism may be activated. The present inventors have previously shown that the HGF/SF receptor associates in vitro, upon autophosphorylation, PI 3-kinase, ras-GAP, PLC-γ and Src-related tyrosine kinases (Bardelli, A., et al., Oncogene 2: 1973-1978 ( 1 99? , ) . Association of PI 3-kinase with the activated receptor has also been found in vivo, in cells stimulated by HGF/SF (Graziani, A., et al., J. Biol. Chem. 266: 22087-22090 (1991)). Recently, the authors have also shown that HGF/SF activates Ras by increasing the turnover between its GDP- and GTP- bound state through the stimulation of a guanine nucleotide exchange factor (Graziani, A., et al., J. Biol. Chem. in press (1993) ) . We have now found that the HGF/SF receptor associates with the proteins She and Gbr2. The mammalian gene She encodes three widely expressed overlapping proteins of 66, 46 and 52 kDa (p66 Shc , p46 Shc and p52 Shc ) containing a C-terminal SH2 domain and a N-terminal collagen-homology region (Pelicci et al. Cell 2-Q: 93-104 (1992)). p46 Shc and p52 Shc are encoded by the same transcript by employing two different ATGs. p66 Shc is encoded by an alterantively spliced transcript (Migliaccio et al. in preparation) . Experimental evidence indicates that She proteins are implicated in the transduction of signals generated by tyrosine kinase receptors. Among these, She proteins are rapidly tyrosine- phosphorilated in response to activation of the EGF (Pelicci et al. ibid) and PDGF (unpublished data) receptors, Erb-B-2 (Segatto et al.. Oncogene 2105-2112 (1993)),, Src and Fps (McGlade et al. Proc. Natl. Acad. Sci. USA 8£: 8869-8873 (1992)). Overexpression of She proteins induces neurite outgrowth in PC12 pheochromocytoma cells, and this effect is blocked by the expression of a dominant-negative Ras mutant (Rozakis-Adcock et al. , Nature 360: 689-692 (1992)). Upon cell stimulation by certain growth factors, She proteins form stable complexes with the Grb2/Sem5 adaptor (Lowenstein et al.. Cell Q 431-442 (1992); Rozakis-Adcock et al.. ibid) . The latter adaptor is known to activate Ras functions by recruiting SoS, a guanine nucleotide exchanger factor (Li et al.. Nature 363: 85-87 (1993); Gale et al.. Nature 363: 88-92 (1993); Rozakis-Adcock et al. Nature 363 : 83-85 (1993); E an et al.. Nature 363: 45-51 (1993); Simon et al.. Cell 21: 169-177 (1993); Oliver et al.. Cell 1: 179-191 (1993)) to the membrane. From the above it clearly appears that the interaction between an activated tyrosine kinase receptor and a cytosolic transducer molecule is a critical step in the signaling pathway leading to cell proliferation and motility. Since these biological responses constitute the most peculiar characteristics of tumor growth and spreading, need for interfering in such interaction is recognized in the art. SUMMARY OF THE INVENTION The present inventors have synthesized a group of phosphopeptides able to interact with intracellular signal transducers thus interfering in the pathways leading to cell proliferation and movement and extracellular matrix invasion. These biological properties can be exploited to inhibit growth of neoplastic cells and to prevent metastatic spreading. The present inventors have also made the following new findings: (1) She proteins bind the tyrosine phosphorylated SF/HGF receptor via the SH2 domain; (2) She proteins bind to phosphotyrosine Y 1349 and Y 1356 of the SF/HGF receptor tail; (3) overexpression of She proteins increases the motogenic response to SF/HGF; (4) She proteins are phosphorylated on Y 317 after binding to the SF/HGF receptor; (5) She proteins phosphorylated on Y 317 form specific complexes with the Grb2 protein; and (6) the Grb2 docking site on She (Y 317 VNV) has the same sequence as signal transducer binding sites on the HGF/SF receptor (YVNV) . Thus, we have synthesized peptides from the Grb2 docking site on She and from the She docking sites containing the recognition motifs Y ,349 VHV and Y 1356 VNV on the hepatocyte growth factor receptor. These peptides are capable of interfering in the pathways leading to cell proliferation and movement and extracellular matrix invansion. Accordingly, the present invention further provides a peptide having the sequence of a portion of She protein, which peptide can bind to a cytosolic signal transducer. The peptide is generally capable of inhibiting binding between She protein and Grb2 protein or between Grb2 and the activated hepatocyte growth factor receptor. Moreover, the present invention provides a peptide having the sequence of a portion of the intracellular region of the human hepatocyte growth faction receptor, which peptide can bind to a cytosolic signal transducer. The peptide is generally capable of inhibiting binding between She protein or the p85 subunit of phosphatidyl inositol 3-kinase and the activated hepatocyte growth factor receptor or between She and other cytosolic signal transducers. Detailed description of the invention The peptides of the present invention are generally tyrosine-containing molecules representing sites of tyrosine phosphorylation. The peptides have a length of, for example, 4 to 20 amino acids, for example 8 to 12 amino acids. The peptides generally reproduce potential recognition motifs for the SH2 domains of intracellular signal transducers. The peptides may have from 4 to 20 amino acids and have the sequence X N -YVN(or H)V-X C wherein X N and X c are each sequences of from 0 to 16 amino acids. Preferably, X N and X c are sequences which flank one of the YVN(or H)V sequences in the HGF/SF receptor and She protein. The interaction of a transducer with activated tyrosine kinase receptor allows recruitment and activation of the transducer itself. The activation of the HGF/SF receptor may be physiological (i.e. as a result of ligand binding and with dimerisation of the receptor), or constitutive (i.e. the receptor is permanently activated even in the absence of ligand) . Constitutive activation may occur in a form of the receptor not having the extracellular ligand binding domain, for example in an oncogenic receptor or following a chromosomal translocation (as in the TPR-MET fusion described herein) . Most intracellular signal transducers have been correlated to cell growth and to oncogenic transformation (Fantl, W.J., et al.. Cell. .69: 413-423 (1992); Reedijk, M. , et al., Mol.Cell. Biol. 1CD: 5601-5608 (1990); Lowenstein, E.J. et al.. Cell 2-0: 431-442 (1992)). Therefore, inhibition of the binding with activated tyrosine kinase receptor or between She protein and other transducers constitutes a means to inhibit cellular mitogenesis and motogenesis, and hence the peptide of the invention may counteract development of a tumor. A preferred embodiment of the invention is a peptide selected from: Position of Tyrosine Phosphopept des in HGF/SF receptor three letter code one letter code sequence 971 H-Tyr*-Asp-Ala-Arg-Val-His-Thr-Pro-OH Y*DARVHTP 1003 H-Tyr*-Arg-Ala-Thr-Phe-Pro-Glu-Asp-OH Y*RATFPED 1026 H-Tyr*-Pro-Leu-Thr-Asp-Met-Ser-Pro-OH Y*PLTDMSP 1093 H-Tyr*-His-Gly-Thr-leu-Leu-Asp-Asn-OH Y*HGTLLDN 1159 H-Tyr*-Met-Lys-His-Gly-Asp-Leu-Arg-OH Y*MKHGDLR 1192 H-Tyr*-Leu-Ala-Ser-Lys-Lys-Phe-Vat-OH Y*LASKKFV 1230 H-Tyr*-Asp-Lys-Glu-Tyr-Tyr-Ser-Val-OH Y*DKEYYSV Position of Tyrosine Phosp-hopeptides in HGF/SF receptor three letter code one letter code sequence 971 H-Tyr*-Asp-Ala-Arg-Val-His-Thr-Pro-OH Y*DARVHTP 1234 H-Tyr*-Tyr-Ser-Val-His-Asn-Lys-Thr-OH Y*YSVHNKT 1235 H-Tyr*-Ser-Val-His-Asn-l_ys-Thr-Gly-OH Y*SVHNKTG 1284 H-Tyr*-Pro-Asp-Val-Asn-Thr-Phe-Asp-OH Y*PDVNTFD 1295 H-Tyr*-Leu-Leu-Gln-Gly-Arg-Arg-Leu-OH Y*LLQGRRL 1307 H-Tyr*-Cys-Pro-Asp-Pro-Leu-Tyr-Glu-OH Y*CPDPLYE 1313 H-Tyr*-Glu-Val-Het-Leu-Lys-Cys-Trp-OH Y*EVMLKCW 1349 H-Tyr*-Val-His-Val-Asn-Ala-Thr-Tyr-OH Y*VHVNATY 1349-1356 H-Tyr*-Val-His-Val-Asn-Ala-Thr-Tyr*-Val- ■ Asn- Y*VHVNATY*VNVK Val-Lys-OH 1356 H-Tyr*-Val-Asn-Val-Lys-Cys-Val-Ala-OH Y*VNVKCVA 1365 H-Tyr*-Pro-Ser-Leu-Leu-Ser-Ser-Glu-OH Y*PSLLSSE wherein Tyr* indicates a phosphorylated or unphosphorylated tyrosine residue. Of the known intracellular signal transducers, PI 3-kinase ' has been demonstrated to bind HGF receptor either in vitro or in vivo upon ligand stimulation. Its recognition motif on the HGF/SF receptor has not yet been determined. Previous work, carried out with the PDGF receptor, had shown that the four amino acids sequence Tyr-Xxx-Xxx-Met (YXXM) , wherein Xxx or X represents any amino acid residue in the three letter code or one-letter code respectively, constitutes the canonical consensus sequence for PI 3- kinase. In the HGF rer-t-rvtor tnere is a potential recognition motif Tyr-Glu-Val-Mec (Y 1313 EVM) , which could represent a binding site for PI 3-kinase. Surprisingly, the experimental results reported hereinbelow show that although the synthetic phosphopeptide containing the consensus Y 1313 EVM is capable of binding to PI 3-kinase, tyrosine 1313 can be eliminated without affecting PI 3- kinase binding. On the contrary, using both the synthetic phosphopeptides of the invention and receptor Tyr-Phe mutants the authors of the present invention have identified the binding sites for PI 3-kinase in the two phosphotyrosines in position 1349 and 1356, as demonstrated by inhibition data obtained using phosphopeptides H-Tyr*-Val-His-Val-Asn-Ala-Thr-Tyr-OH, H- Tyr*-Val-Asn-Val-Lys-Cys-Val-Ala-OH and H-Tyr*-Val-His-Val- Asn-Ala-Thr-Tyr*-Val-Asn-Val-Lys-OH. These residues thus identify Tyr-Val-(Asn or His)-Val [YV(N or H)V] as a novel recognition motif for PI 3-kinase and the corresponding phosphopeptides can be usefully employed as inhibitors of the binding of the HGF receptor with PI 3- kinase. A particularly preferred embodiment of the present invention is therefore a phosphopeptide having the formula H-Tyr*-Val- His-Val-Asn-Ala-Thr-Tyr-OH or H-Tyr*-Val-Asn-Val-Lys-Cys- Val-Ala-OH or H-Tyr*-Val-His-Val-Asn-Ala-Thr-Tyr*-Val-Asn- Val-Lys-OH, wherein Tyr* indicates a residue of phosphorylated tyrosine. A further preferred embodiment of the invention is the peptide H-Asp-Asp-Pro-Ser-Tyr*-Val-Asn-Val-Gln-OH (DDPSY*VNVQ) wherein Tyr* (Y*) represents phosphorylated or unphosphorylated tyrosine. The peptides of the invention may be provided in the form of pharmaceutically acceptable salts. Suitable salts include base salts such as alkali metal salts (e.g. sodium or potassium salts) and ammonium salts; and acid addition salts such as hydrochloride and acetate salts. The peptides of the invention can be synthesized according to standard method such as those described in Escobedo, J.A., et al., Mol. Cell. Biol. ϋ: 1125-1132 (1991) or Turck, C.W. Peptide Res. 5_: 156-160 (1992) , for example using a protected prephosphorylated tyrosine residue. In particular the peptides can be prepared by liquid or solid-phase methodologies known to those skilled in the art. (Schroeder et al., "The Peptides", Vol. I, Academic Press 1965, or Bodanszky et al., "Peptide Synthesis", Interscience Publishers, 1966, or McOmie (ed.) "Protective Group in Organic Chemistry", Plenum Press, 1973, or Barany et al., "The Peptides: Analysis, Synthesis, Biology" 2 , Chapter 1, Academic Press, 1980) . Thus, the invention includes a process for preparing a peptide of the invention, which process comprises chemically synthesizing the peptide from single amino acids and/or preformed peptides of two or more amino acid residues. When it is wished to prepare a peptide in which a tyrosine residue is phosphorylated, a prephosphorylated protected tyrosine residue may be introduced during a solid phase synthesis, or a tyrosine residue of a protected preformed peptide may be phosphorylated while the peptide is attached to a solid support. In the case of solid-phase synthesis any manual or automatic peptide synthesizer can be used and the peptides can be assembled in a stepwise manner on a resin support using either Boc or Fmoc strategies. All the reagents used as starting materials are on the market or may be produced and purified in accordance with methods known in the art. When preparing a phosphopeptide, in order to avoid cleavage of the phosphate group during deprotection of the protected peptides, a solution of trifluoromethane sulfonic acid- trifluoroacetic acid containing a suitable mixture of scavangers is used. The deprotected peptides are purified by reverse phase high performance liquid chromatography on a C18-Vydac column (Hesperia Calif.) in 0.1% trifluoroacetic acid by using a linear gradient of acetonitrile, and are isolated by lyophilization. All phosphopeptides are obtained as polihydrated polytrifluoroacetates. The peptide content of all products is 65 to 90% and the chromatographic purity is more than 95% by HPLC peak relative integration at λ=225 nm. Amino acid ' analysis were carried out on acid hydrolysates (110°C for 22 h in 6 N HC1 + 0.1% phenol). Alternatively a peptide containing a non-phosphorylated tyrosine can be first synthesized and subsequently a phosphate group can be introduced on the tyrosine residue either enzymatically or by chemical methods (in such a case the other functions susceptible of reaction with the phosphorylating agent must be suitably protected) . In this specification, the abbreviations used for amino acids and protecting groups are based on recommandations of the IUPAC-IUB Commission on Biochemical Nomenclature (see Eur. J. Biochem., vol 138, 9-37, 1984). In particular, the following abbreviations were used throughout the text: Boc, t-butyloxycarbonyl; tBu, t-butyl; Bzl, benzyl; C1Z, 4-chloro benzyloxycarbonyl; DPCDI, diisopropylcarbodiimide; DCM, dichloromethane, DMF, dimethylformamide; Dnp, dinitrophenyl; Fmoc, 9-fluorenylmethoxycarbonyl; RP-HPLC, reverse phase high performance liquid chromatography; Trt, trityl. The capacity of the phosphopeptides of the invention to inhibit the binding of intracellular transducers to the tyrosine kinase receptor or to She protein can be assessed by competition experiments as shown in the experimental section for the binding to the tyrosine kinase receptor. A further demonstration of the biological significance of the autophosphorylation sites on the tyrosine kinase receptor is provided by the focus formation assay described in the experimental section. In particular, this assay demonstrates how the transforming activity of the native activated HGF receptor can be efficiently inhibited by mutating the specific autophosphorylation sites under consideration on the receptor itself (Tyr-Phe mutation) . A peptide reproducing one of the phosphorylation sites of HGF/SF receptor or She can then interfere with binding of transducers thus inhibiting the downstream transmission of the mitogenic and motogenic signal. The peptides of the invention can therefore be used in the treatment of the human or animal body by therapy, for example in the treatment of a neoplastic disease. The peptides of the invention are phosphorylated or unphosphorylated. The active form of the peptides is generally phosphorylated, but it may be advantageous to administer a peptide in unphosphorylated form and allow the peptide to become phosphorylated inside the body of the patient. This is because the peptides may be more easily taken up into " cells when unphosphorylated. The peptides of the invention may be administered to a patient by any convenient parenteral route as such or properly conjugated in order to increase enzymatic stability and cell permeability. The choice of whether subcutaneous, intravenous or intramuscular administration is adopted; of the dose.; c-i the frequency of administration depends upon a variety of factors. These factors include the purpose of the administration, the age and weight of the patient being treated and the condition of the patient. A therapeutically effective amount is given. Typically, however, the peptide is administered in an amount of from 10 to 1000 μg per dose, more preferably from 50 to 500 μg per dose, for each route of administration. The peptide may be formulated in a pharmaceutical composition. The pharmaceutical composition also comprises a pharmaceutically acceptable carrier or diluent. Any appropriate carrier or diluent may be employed, depending upon the route of administration. The following Example illustrates the invention. In the accompanying drawings: Figure 1. Inhibition of binding of p85 to HGF/SF receptor by tyrosine-phosphorylated peptides. Recombinant HGF/SF receptor was purified by immunoprecipitation from baculovirus-infected Sf9 cells using a rabbit polyclonal antiserum and phosphorylated with cold ATP. Lysates of Sf9 cells expressing p85 were pre-incubated with each of the phosphopeptides (10 μM) . The lysates were then allowed to associate with immobilized recombinant HGF/SF receptors. Following association the complex was washed and receptor- bound p85 was detected by an in vitro kinase assay, as described in Materials and Methods of Example 4. The phosphopeptides are identified by the number of the amino terminal tyrosine. Figure 2. Inhibition of binding of p85 to HGF/SF receptor with different concentrations of tyrosine-phosphorylated peptides. The phosphopeptides which efficiently out-competed p85 binding to the HGF/SF receptor (Fig. 1) were used at increasing concentrations (10 nM, 100 nM, 1 μM from left to right) to define their relative affinities for p85. Conditions of the experiment were as in Fig. 1. Phosphopeptide 1365 was used as a negative control for p85 interaction. Figure 3. Inhibition of binding of PI 3-kinase holoenzyme to HGF/SF receptor by tyrosine-phosphorylated peptides. The phosphopeptides which efficiently out-competed p85 (Fig. 1) were assayed for the ability to interfere with binding of the PI 3-kinase holoenzyme to the HGF/SF receptor. Cytosolic extracts from three days-starved A549 cells were pre- incubated with each of the phosphopeptides (10 μM) prior to incubation with the immobilized recombinant HGF/SF receptor. The presence of receptor-associated PI 3-kinase in the immunocomplexes was determined by PI 3-kinase activity assay, as described in Materials and Methods of Example 4. The position of the phosphatidylinositol-3-phosphate (PIP) product of the PI 3-kinase reaction is indicated. SUBSTITUTE SHEET(RULE 21) Figure 4. Effects of Tyr-Phe mutations on the interaction of HGF/SF receptor with p85. COS 7 cells were transfected with plasmids encoding wild type HGF/SF receptor (wt) or receptors in which the tyrosine codon at the indicated position was converted to a phenylalanine codon individually, or in combination. COS 7 cells express endogenous HGF/SF receptor. However, the simian protein is not recognized by a monoclonal antibody directed against the carboxyl-ter inal human-specific peptide. These antibodies were used to selectively immunoprecipitate the human HGF/SF receptor from transfected COS 7 cells. Immobilized pre¬ phosphorylated receptors were incubated with lysates of Sf9 cells expressing p85. In panel A both the receptor and p85 were labelled by an in vitro kinase assay as described in Materials and Methods of Example 4. In panel B the presence of p85 in the receptor immune-complex was determined by immunoblot using anti-p85 monoclonal antibodies. Figure 5. In vivo effect of Tyr-Phe mutations on the interaction of the HGF/SF receptor with the PI 3-kinase holoenzyme. COS 7 cells expressing wild type or mutated receptors were stimulated with HGF/SF and lysed. Receptors were immunoprecipitated with human-specific monoclonal antibodies. In panel A and B the presence of the receptor- associated PI 3-kinase was determined by PI 3-kinase activity assay, as described in Materials and Methods of Example 4. The position of the phosphatidylinositol-3- phosphate (PIP) product of the PI 3-kinase reaction is indicated. Panel C and D show by im unoblot (using human- specific monoclonal antibodies) that the samples tested for PI 3-kinase activity contained equivalent amounts of recombinant receptor. The TK " receptor mutant has been obtained converting the aspartic acid at position 1204 to an asparagine residue. This results in a kinase-inactive HGF/SF receptor. Figure 6. Identification of Y 1349 and Y, 3S6 as in vitro phosphorylation sites in the HGF/SF receptor by tryptic phosphopeptide mapping. Profile A shows the HPLC analysis at 214 nm of a synthetic non-phosphorylated peptide (I24K) , which corresponds to the tryptic peptide containing tyrosine Y, 349 and Y, 356 in the HGF/SF receptor. I24K elutes from the HPLC column after 65 minutes. B and C show the radio-HPLC elution profiles of tryptic phosphopeptides derived from in vitro [7- 32 P]ATP-phosphorylated wild type receptor (B) and the Phe 1349 ., 356 receptor mutant (C) . Figure 7. Evaluation of the relative affinities of phosphotyrosine 1313, 1349 and 1356 for the N- and C- SH2 domains of p85. Affinities were determined by biospecific interaction analysis with the BIAcore instrument (Jonsson, U. , Fagerstam, L. , Roos, H. , Ronnberg, J., Sjolander, Stenber, E. , Stahlberg, R. Urbaniczky, C. , Ostlin, H. , and Malmquist. 1991. Surface plasmon reasonance and microfluidics for real time biospecific interaction analysis. Biotechniques 11:520-527; Jonsson, U. and M. Malmquist. 1992. Real time biospecific analysis. The integration of surface plasmon reasonance detection, general biospecific interface chemistry and microfluidics into one analytical system p. 291-336. In F. Turner (ed) , Advances in Biosensors, vol. 2 JAI Press, London; Karlsson, R. , Michaelsson, A., and L. Mattsson. 1991. Kinetic analysis of monoclonal antibody-antigen interactions with a new biosensor based analytical system. J. Immunol. Meth. 145:229-246) . Relative affinities were determined by measuring the ability of the phosphopeptides to inhibit the interaction of the SH2 domains with an immobilized phosphopeptide (DMSKDESVDY*VPMLDMK) which includes Y 7S1 in the human PDGF receptor. Panel A and B show the results of these measurements, expressed as % inhibition of binding to phosphopeptide Y751. Panel C, shows the phosphopeptide concentrations necessary to reach half-maximal inhibition of binding. Figure 8. Focus Formation Assay with different TPR-MET constructs. In TPR-MET 1349 , TPR-MET Phe 1356 and TPR-MET phe 1349 " 1356 the tyrosine residues corresponding to Tyr 1349 and/or Tyr 1356 of the HGF/SF receptor were mutagenized to phenylalanine. Figure 9. SF/HGF induces phosphorylation of She and association with SF/HGF receptor and Grb2. A549 cells, either control or expressing the Y 317 →F mutant She cDNA (A549/Y317F) , were grown to confluence, serum starved for 24 hours and lysed. Where indicated (+) , cells were stimulated for 5' with 200 U/ml of pure SF/HGF. Immunoco plexes, precipitated with the first antibody (IPP) , were resolved on 9% SDS-PAGE and analyzed by immunoblot with a second antibody (WB) , as indicated. Arrows point the endogenous She isoforms (p46, p52, p56) , the SF/HGF receptor β chain (pl45) , the transfected tagged mutant She isoforms (p53 and p58) and the Grb2 protein (p23) . Figure 10. Association and tyrosine phosphorylation of She are dependent on SF/HGF receptor kinase activity. Lysates of COS-1 cells transiently expressing the cDNAs of wild-type SF\HGF receptor (WT) or of a kinase-defective receptor mutant (LYS " ) were immunoprecipitated with either anti-Met monoclonal antibody (A. and B.) or an anti-She polyclonal sera (C. and D.), western blotted and probed with either anti-Met or anti P-Tyr antibodies, as indicated. Arrows indicate the precursor protein (pl70) that in COS-1 cells is the predominant, fully functional, form of the SF/HGF receptor (Ponzetto et al., Mol. Cell. Biol. 13.: 4600-4608 (1993)); p46, p52 and p56 are She isoforms. Figure 11. Binding of She and Grb2 SH2 domains to proteins solubilized from SF/HGF treated cells. Lysates were prepared from confluent monolayers of unstimulated (-) or SF/HGF stimulated (+) A549 cells. Association experiments were carried out incubating total cell protein with recombinant GST-SH2.Shc (A.) or GST-SH2.Grb2 (B.) immobilized onto glutathione Sepharose. The bound proteins were eluted and analyzed in western blot using the indicated antibodies. Figure 12. Mapping of She binding sites on the SF/HGF receptor. COS-1 cells expressing SF\HGF receptors, either (WT) or mutated Y →F at the residues indicated on the top of each line, were co- immunoprecipitated with anti-She antibodies, blotted and revealed by anti-Met antibodies. The arrow indicates the receptor precursor (pl70) . Figure 13. The She SH2 domain binds to the docking site of the SF/HGF receptor <γ ,35β ) but not to its own (Y 317 ) . The same concentration of Shc-SH2 was injected over two biosensor surfaces on which two phosphopeptides had been immobilised. Y1356P is derived from the sequence VNATY ,356 VNVK of the receptor tail; Y317P is derived from the sequence DDPSY 317 VNVQ. Note that both peptides contain the same core (YVNV) but different upstream sequences. The initial rapid increase in the response is due to the "bulk effect" of the injected solution. Figure 14. Overexpression of She enhances the motogenic response to SF/HGF. Blind-well Boyden chambers were assembled with polycarbonate filters (8μm pores) coated with gelatine. The cells were labelled with 5-[ 125 I]iodo-2'-deoxyuridine (see Methods) and plated in the upper chamber. The lower chamber was filled with serum-free medium supplemented with the indicated concentrations of purified SF/HGF. After 6 h of incubation at 37°C, cells attached to the upper side of the filters were mechanically removed; the cells migrated to the lower side of the filter were fixed and quantitated in a 7-counter (Y axes: CPM bound) . The lower panel shows a low-magnification micrograph picture (4x) of cells migrated to the lower side of the filters in the presence of 40 U/ml of SF/HGF. Cells were either infected with a retrovirus carrying the SHC cDNA (SHC-plXSN) , or with the empty virus (MOCK) . Figure 15. The Grb2 SH2 domain binds to the Y 317 docking site of She. Panel A: sensorgrams obtained by injection of a range of Gst-SH2.Grb2 concentrations over the immobilised phosphopeptide derived from the She sequence DDPSY 3,7 VNVQ. Panel B: effect of competing peptide on the dissociation rate. At the end of the Grb2 injection, buffer or 20 M of non-biotinylated phosphopeptide were injected. Panel C: analysis of the data shown in panel A. The figure on the left is a plot of the rate of binding versus the relative response for the six different sensorgrams. In the figure on the right, the slopes of each line are plotted against the concentration: the new slope gives the value of the association rate constant. Figure 16. A model of the interactions between the SF/HGF receptor and the SH2 containing adaptor molecules She and Grb2. Grb2 binds with high affinity with the docking site Y 1356 VNV on the receptor tail. The adaptor molecule She can interact with either phosphotyrosine Y 1349 or y"* 6 . Upon binding. She is transphosphorylated by the receptor on Y 317 , re-creating a high affinity docking site for Grb2. The receptor may thus activate the motogenie response through the She pathway, without interfering with the Ras-mediated mitogenic response driven by Grb2-SoS. SUBSlliϋTE SHEET(RULE 26) EXAMPLE 1 Preparation of H-Tyr*-Val-His-Val-Asn-Ala-Thr-Tyr-OH (Formula I) 0.89g (0.5 mmol.) of Fmoc-Tyr(tBu) -4-(oxymethyl) phenoxymethyl-copoly(styrene-1% divinylbenzene) resin (0.56 mmol/g) were subjected to the following cycle, steps (1) to (5) , of treatments: (1) DMF (2) piperidine (20%) in DMF (3) DMF (4) preformed 1-hydroxybenzotriazole ester (2.0 mmol) of Fmoc-amino acid in DMF Volumes of washes and reagents were 10 to 20 ml. Each step was repeated as many times as necessary for either complete reaction of the resin (steps 2,4) or complete displacement of the previous reagent from the resin (steps 1, 3, 5). Samples of resin were taken after each cycle and checked for completeness of reaction by a ninhydrin test. 1-hydroxybenzotriazole esters of Fmoc-amino acids were formed just prior to use by reacting Fmoc-amino acid (2.0 mmol.), 1-hydroxybenzotriazole (2.0 mmol.) and DPCDI (2.0 mmol. ) in DMF. The cycle of reactions, (1) to (5) , was repeated for each amino acid residues such as to provide the sequence of formula I. The following protected amino acids were added in the order: Fmoc-Thr(tBu)-OH, Fmoc-Ala-OH, Fmoc-Asn-OH, Fmoc-Val-OH, Fmoc-His(Trt)-OH, Fmoc-Val-OH and Boc-Tyr (P03Bzl2) -OH. After the last cycle the peptidyl resin was washed several times with DCM and dried. A weight gain of 0.54 g was obtained with respect to the starting resin. 1.0 g of the peptidyl resin was stirred with 20 ml of a mixture of trifluoromethanesulfonie aeid/trifluoroaeetic acid/dimethyl-sulfide/ethanedithiol (20:50:3:3:1) for 3 h at 0°C. Deprotected peptide was precipitated with 1 liter of diethylether and collected by filtration. The crude peptide was purified by RP-HPLC on a C18-Vydac (Hesperia, CA) column (2,2 x 25 cm) in 0.1% trifluoroacetic acid using a linear gradient of acetonitrile from 0-65 % over 90 min. Fractions containing the product in pure form were combined, the acetonitrile was evaporated in vacuo and the remaining solution was lyophilized. It was obtained 132 mg of the compound of formula I with chromatographic purity (HPLC) of 95.7%. Amino acid ratios: Ala 1(1); Asp 1.07(1); His 0.96(1); Thr 0.91(1); Tyr 1.88(2); Val 2.03(2). Peptide content: 73.7%. FAB mass spectroscopy; m/z 1044.4 [M-H]' EXAMPLE 2 Preparation of H-Tyr*-Val-Asn-Val-Lys-Cys-Val-Ala-OH (Formula II) Starting from 0.5 mmol of Fmoc-Ala-4-(oxymethyl) phenoxymethyl-copoly(styrene-1% divinylbenzene)resin and adding the protected amino acids in the following order: Fmoc-Val-OH, F oc-Cys(Trt)-OH,Fmoc-Lys(Boc)-OH, Fmoc-Val-OH, Fmoc-Asn-OH, Fmoc-Val-OH, Boc-Tyr-OH, the dephosphopeptide was assembled on the resin in the same manner as described in the example 1. After the last cycle the phosphorylation of Tyr residue was obtained directly on the peptide still attached on the resin by treatment of the peptidyl resin with a solution of 30 eq. of lH-tetrazole and 10 eq. of di-ter-butyl-N,N-diisopropyl- phosphoramidite in DMF for 1 h at 25°C and subsequently with 20 eq. of ter-butylhydroperoxide in toluene for 1 h at 25°C. The cleavage, the protecting groups removal and the purification of crude product were carried out on 1.0 g of peptidyl resin as described in example 1. Amino acid ratios: Ala 1(1); Asp 1.02(1); Cys nd(l); Lys 0.99(1); Tyr 0.95(1); Val 2.98(3). Peptide content: 68.9%. FAB mass spectroscopy: m/z 973.4 [M-H]" EXAMPLE 3 Preparation of H-Tyr*-Val-His-Val-Asn-Ala-Thr-Tyr*-Val-Asn- Val-Lys-OH (Formula III) 0.74 g (0.5 mmol) of Boc-Lys(C1Z) -4-(oxymethyl) phenylacetamido-methyl-copoly(styrene-1% divinylbenzene) resin (0.68 mmol/g) were subjected to the following cycle, steps (1) to (7) , of treatments: (1) DCM (2) trifluoroacetic acid (50%) in DCM (3) DCM (4) diisopropylethyla ine (5%) in DMF (5) DMF (6) preformed 1-hydroxybenzotriazole ester (2.0 of Boc- amino acid in DMF (7) DMF Each step was repeated as many times as necessary for either complete reaction of the resin (steps 2,4,6) or complete displacement of the previous reagent from the resin (1,3,5,7). Samples of resin were taken after each cycle and checked for completeness of reaction by ninhydrin test. 1-hydroxybenzotriazole esters of Boc-amino acids were formed just prior to use by reacting Boc-amino acid (2.0 mmol.) , 1- hydroxybenzotriazle (2.0 mmol.) and DPCD1 (2.0 mmol.) in DMF. The cycle of reactions, (1) to (7) , was repeated for each amino acid residue such as to provide the sequence of formula III. The following protected amino acids were added in the order: Boc-Val-OH, Boc-Asn-OH, Boc-Val-OH, Boc-Tyr(P03Bzl2) -OH, Boc-Thr(Bzl)-OH, Boc-Ala-OH, Boc-Asn-OH, Boc-Val-OH, Boc- His(Dnp)-OH, Boc-Val-OH and Boc-Tyr(P03Bzl2)-OH. At the completion of the synthesis of His(Dnp) protecting group was removed with 15 ml of 1 M thiophenol in DMF directly on the peptide still attached on the resin, then the peptidyl resin was washed several times with DCM and dried. 1.51 g of peptidyl resin were obtained. The cleavage, the protecting groups removal and the purification of the crude product were carried out on 1.0 g of starting peptidyl resin as described in example 1. It was obtained 196 mg of compound III with chromatographic purity (HPLC) of 95.9%. Amino acid ratios: Ala 1(1); Asp 1.99(2); His 1.05(1); Lys 0.97(1); Thr 0.93(1); Tyr 1.85(2); Val 4.01(4). Peptide content: 71.1%. FAB mass spectroscopy: m/z 1564.62 [M-H] ' . EXAMPLE 4 Materials and Methods Reagents, cells, antibodies. All reagents, unless specified, were purchased from Sigma Chemical Co. Protein A covalently coupled to Sepharose was purchased from Pharmacia LKB Biotechnology Inc.. All radioactive isotopes were purchased from Amersham Corp. A549 lung carcinoma cells and COS-7 cells, purchased from ATCC (CCL 185) (American Type Culture Collection) , were grown in DMEM medium supplemented with 10% foetal calf serum (Flow Laboratories, Inc.) in a 5% C0 2 - water-saturated atmosphere. Spodoptera fruqiperda (Sf9) cells, from ATCC (CRL 1711) , were grown in monolayers cultures using SF-900 medium (GIBCO BRL) . Antisera and monoclonal anti-Met antibodies were raised against a synthetic peptide corresponding to the nineteen C-terminal amino acids of the human MET sequence (Prat, M. , et al., Mol. Cell. Biol. ϋ (12): 5954-5962 (1991)). Antibodies against p85 are described by Otsu et al. (Otsu, M. , et al.. Cell 65: 91-104 (1991)). The synthetic phosphopeptides were synthesized with the procedure described in Example 1 to 3. Expression of HGF/SF receptor and p85 cDNAs in insect cells using baculoviruses vectors. Recombinant HGF/SF receptor and p85 baculoviruses were constructed as previously described (Bardelli, A., et al., Oncogene 1: 1973-1978 (1992); Otsu, M., et al.. Cell 6J5: 91-104 (1991)) and used to infect Sf9 cells (Piwnica-Worms, H. et al., J. Virol. 6 : 61-6 (1990)). GST-SH2 domain fusion proteins. The N- and C- SH2 domains of the bovine PI 3-kinase p85 subunit (amino acids 314-431 and 612-722) were obtained by polymerase chain reaction and cloned into the pGEX-2 bacterial expression vector (Smith, D.B., and Johnson K.S., Gene 67: 31-40 (1988). Glutathione-S-transferase (GST)-SH2 fusion proteins were purified from bacterial lysates by glutathione affinity chromatography (Panayotou, G. , et al. EMBOJ., JL1: 4261-4272 (1992)). Amino acid analysis on an Applied Biosyste s 420A analyzer was used to determine the concentration of the recombinant proteins. Site-directed mutagenesis and expression in COS 7 cells of the MET cDNA. The cloning of the MET cDNA has been reported previously (Ponzetto, C, et al., Oncogene 6.: 553-559 (1991), EMBL Data-Bank reference n° X54559) . The 3' end fragment from nucleotide 2355 to the end was subcloned in pSELECT™-l. Site-directed mutagenesis was performed using an in vitro oligonucleotide site-directed mutagenesis system (Altered Sites™ in vitro Mutagenesis System, Promega) . Oligonucleotides were synthesized using an Applied Biosystem 391 apparatus. Mutant clones were identified by sequencing (T7 sequencing kit from Pharmacia) . Full size MET cDNAs carrying the appropriate Tyr-Phe mutation were reconstructed in the PMT2 vector which contains the major late Adenovirus promoter. All plasmids were transfected by lipofectin (GIBCO BRL) in COS 7 cells. In vitro association experiments. Sf9 cells expressing the recombinant HGF/SF receptor (approximately 4xl0 6 cells/ point) were lyseu 36 hours after infection in buffer A (10 mM Tris-HCl buffer pH 7.5, 10% glycerol, 1% Triton X-100, 150 mM NaCl, 5 mM EDTA), supplemented with 0.2 mM phenyl- methylsulfonyl fluoride, 1 μg/ml leupeptin, 0.1 TlU/ml aprotinin and 1 μg/ml pepstatin. Lysates were clarified at 15,000 x g at 4°C for 15 minutes and the supernatants immunoprecipitated after 2 hours incubation with anti-Met antibodies coupled to Protein A-Sepharose. Immunocomplexes were washed three times with buffer A, once with buffer B (10 mM Tris-HCl pH 7.4, 100 mM NaCl, 1 mM EDTA) and once with buffer C (25 mM 4-(2-hydroxyethyl)-1-piperazine- ethanesulfonic acid (HEPES) buffer pH 7.2, 100 mM NaCl, 5 mM MgCl 2 ) . Samples were pre-phosphorylated by incubation for 15 minutes at 25°C in buffer C with 10 μM unlabelled ATP and then washed three times with cold buffer A supplemented with 1 mM sodium ortho-vanadate. Association between the immobilized receptor and the baculovirus-expressed p85 was carried out as previously described (Bardelli, A., et al., Oncogene 7:1973-1978 (1992)). For the association experiments with the PI 3-kinase holoenzyme three days serum-starved A549 cells (approx.2xl0 6 cells/point) were used as a source of PI 3-kinase. A549 cells were Dounce- homogenized in MOPS buffer (20 mM 3-(N- morpholino)propanesulfonic acid) (pH 7.5), 1 mM MgCl 2 , 0.1 mM EDTA, 200 mM sucrose, 1 mM sodium ortho-vanadate) , supplemented with 0.2 mM phenylmethylsulfonyl fluoride, 1 μg/ml leupeptin, 0.1 TlU/ml aprotinin and 1 μg/ml pepstatin-, Homogenates were centrifuged at 100,000 x g for 20 minutes at 4°C. When checking for the ability of phosphopeptides to block the association with the receptor, cell lysates were pre-incubated with the phosphopeptides for 1 hour at 4°C prior to incubation with the immobilized recombinant HGF/SF receptor. Following association, immunocomplexes were washed three times with buffer A, twice with buffer D (0.5M LiCl, 100 mM Tris-HCl pH 7.6), and twice with buffer B. The presence of the p85 subunit of the PI 3-kinase in the receptor immunoprecipitate was determined by: i) labelling of the receptor and associated proteins with [7~ 32 P]ATP by jln vitro kinase assay; ii) Western immunoblotting; iii) PI 3- kinase activity assay. In vivo association experiments. Transfected COS 7 cells expressing HGF/SF receptor mutants were stimulated for 10 minutes at 37°C with HGF/SF (12 ng/ml) and lysed in buffer A in the presence of ImM sodium ortho-vanadate. Lysates were clarified at 15,000 x g at 4°C for 15 minutes and the supernatants immunoprecipitated after 2 hours incubation with anti-Met antibodies specific for the human protein coupled to Protein A-Sepharose. Complexes were washed twice with buffer A, twice with buffer D, and twice with buffer B. The presence of the receptor-associated PI 3-kinase in the complex was determined by PI 3-kinase assay as described by Whitman et al. (Whitman, M. , et al., Nature 315:239-242 (1985)) . In vitro kinase assay. Receptor-associated proteins were labelled in 20 μl of buffer C, in the presence of 10 μCi [7- 32 P]ATP (specific activity 7,000 Ci/M ; Amersham) at 25°C for 15 minutes. The reaction was stopped by adding 1 ml of ice- cold Buffer A without protease inhibitors. Samples were washed three times with cold buffer A. The labelled immunocomplexes were eluted from Protein A-Sepharose in boiling Laemmli buffer. Supernatants were then subjected to 8% sodium dodecyl-sulfate polyacrylamide gel electrophoresis (SDS-PAGE) . Western immunoblotting. Im unoprecipitates after the association were solubilized in boiling Laemmli buffer, separated on 8% SDS-PA^E and electro-transferred into nitrocellulose filters (Hi-bond, Amersham) . Filters were then incubated with the indicated antibodies and specific binding was detected by the enhanced chemiluminescence system (ELC™, Amersham) . Tryptic phosphopeptide mapping. 32 P-labelled bands corresponding to in vitro-phosphorylated wild type and mutant HGF/SF receptors were excised from polyacrylamide gels and treated as previously described (Ferracini, R. , et al., J. Biol. Chem. 266:19558-19564 (1991)). Tryptic peptide digests were dissolved in 100% dimethylformamide, diluted to 50% with the HPLC loading buffer (0.1% trifluoroacetic acid in water) and separated by high performance liquid chromatography (HPLC) on a reverse phase C 2 /C 18 Superpack Pep- S column (Pharmacia) with a gradient of acetonitrile (0-32% in 70 minutes) in the presence of 0.1 trifluoroacetic acid. with a flow of 1 ml/minute. The eluted radioactivity was monitored by a Radiomatic A-100 radioactive flow detector (Packard Instrument Co.). As a control, a synthetic peptide (I24K, neosystem Laboratories) , was separated on HPLC as above and analyzed at 214 nm. I24K encompasses 24 amino acids from Isoleucine 1337 to Lysine 1360 of the Met protein sequence, and thus corresponds to the predicted tryptic phosphopeptide of interest, except for the fact that it is not phosphorylated. Analysis of the interaction of Y I349 and Y 13S6 with the p85 N- and C- SH2 domains using the BIAcore. Details of the construction and principle of operation of the BIAcore biosensor have been described (Jonsson, U. , et al., Biotechniques ϋ:520-527 (1991); Jonsson, U. , and M. Malmquist. 1992. In F. Turner (ed) , Advances in Biosensor, vol. 2 JAI Press, London (1992); Karlsson, R. , et al., J. Immunol. Meth. 145:229-246 (1991)). The SH2 domains used in these experiments were desalted through a Pharmacia column on a SMART chromatography system in order to achieve buffer exchange to the BIAcore running buffer, consisting of 20 mM Hepes, pH 7.4, 150 mM NaCl, 3.4 mM EDTA, 0.005% Tween 20 and 4 mM DTT. Avidin (Boehringer) at 50 μg/ml in 20 mM sodium acetate buffer, pH 4.0, was immobilized on the sensor chip surface after activation with a 1:1 mixture of N- hydroxysuccini ide (NHS) and N-Ethyl-N'-(3-dimethyl- aminopropyl)-carbodiimide hydrochloride (EDC) (Pharmacia). Excess reactive groups were blocked with ethanolamine (1.0M). Biotinylated phosphopeptide Y751 (DMSKDESVDYVPMLDMK) was injected over the avidin at a flow rate of 5 μg/sec for 50 seconds. Non-specifically bound material was removed with a short pulse (4 seconds) of 0.1% SDS. GTS-SH2 domain fusion proteins were mixed with a range of concentrations of HGF/SF receptor phosphopeptides and injected over the surface at 5 μl/min for 40 seconds at a constant temperature of 25°C. The material bound to the surface was removed with a 4 seconds pulse of 0.1% SDS, which brought the signal to background level. RESULTS Competition experiments with synthetic phosphopeptides. In our initial studies we made use of synthetic phosphopeptides to outcompete p85 or PI 3-kinase in in vitro association experiments with the recombinant HGF/SF receptor. The phosphopeptides were designed to cover all the possible tyrosines present in the cytoplasmic portion of the HGF/SF receptor. The list of the phosphopeptides is shown above in the section entitled "Detailed description of the invention". Sixteen phosphopeptides were eight amino acids long and began with a phosphotyrosine residue at the N- terminus. One phosphopeptide was twelve amino acids long and included two phosphotyrosines. Previous work carried out with the PDGF receptor had shown that the four amino acids located immediately downstream to the phosphotyrosine are important for defining the SH2 recognition site (Fantl, W.J., et al.. Cell 69: 413-423 (1992)). In the experiment shown in Fig. 1 we used lysates of insect cells (Sf9) infected with a recombinant baculovirus as a source of p85 protein (Otsu, M. , et al.. Cell 65:91-104 (1991)) . Such lysates were diluted appropriately (see Materials and Methods) and pre-incubated with each of the phosphopeptides (10 μM) before incubation with the HGF/SF recombinant receptor. The receptor was immunoprecipitated from lysates of Sf9 cells infected with a recombinant baculovirus carrying a full-size human MET cDNA (Bardelli, A., et al. Oncogene 7:1973-1978 (1992)). In these cells the receptor is synthesized largely in the form of the uncleaved precursor (MET Ba( . in the Figures) which is, however, fully functional (Bardelli, A., et al. Oncogene 7:1973-1978 (1992) ) . The receptor was immobilized on protein-A Sepharose beads, and pre-phosphorylated with cold ATP. After association, the beads were washed and the complexes were phosphorylated with [7~ 32 P]-ATP. During the phosphorylation reaction both the receptor and p85 become labelled, and thus detectable in SDS-PAGE. Fig. 1 shows that only three of the phosphopeptides efficiently outcompeted p85: H-Tyr*-Glu-Val- Met-Leu-Lys-Cys-Trp-OH, H-Tyr*-Val-His-Val-Asn-Ala-Thr-Tyr- OH, H-Tyr*-Val-Asn-Val-Lys-Cys-Val-Ala-OH. Thephosphopeptide H-Tyr*-Val-His-Val-Asn-Ala-Thr-Tyr*-Val- Asn-Val-Lys-OH also completely prevented p85 binding, while phosphopeptide H-Tyr*-Cys-Pro-Asp-Pro-Leu-Tyr-Glu-OH was only partially effective. In the experiment shown in Fig. 2 we sought to roughly define the relative affinities of these phosphopeptides for p85. The experiment was carried out as the previous one, but the phosphopeptides were used at concentrations varying between 10 nM and 1 μM. The efficiency at outcompeting p85 was highest for H-Tyr*-Glu- Val-Met-Leu-Lys-Cys-Trp-OH, followed by H-Tyr*-Val-Asn-Val- Lys-Cys-Val-Ala-OH, H-Tyr*-Val-His-Val-Asn-Ala-Thr-Tyr-OH, and H-Tyr*-Cys-Pro-Asp-Pro-Leu-Tyr-Glu-OH. The phosphopeptide H-Tyr*-Val-His-Val-Asn-Ala-Thr-Tyr*-Val- Asn-Val-Lys-OH seemed to be comparable to H-Tyr*-Val-Asn- Val-Lys-Cys-Val-Ala-OH in its affinity for p85. Since the interaction with the pllO catalytic subunit could affect the conformation of p85, these results might not reflect the true properties of the SH2 domains of p85 in the complex. To exclude this possibility we carried out the same kind of competition experiments using lysates of A549 cells as a source of PI 3-kinase holoenzyme. The association between the holoenzyme and the recombinant receptor was visualized measuring the PI 3-kinase activity in the receptor complexes. Fig. 3 shows that the phosphopeptides which had proven capable of outcompeting p85 also interfere with binding of the PI 3-kinase holoenzyme to the HGF/SF receptor. In particular it should be noted that the phosphopeptide including both phosphotyrosine 1349 and 1356 seems to be more efficient at displacing the PI 3-kinase holoenzyme from the HGF/SF receptor than those including just one of these residues. The results of this first set of experiments suggested the possible existence of a double binding site for PI 3-kinase in the HGF/SF receptor, consisting of the phosphotyrosine pairs 1307-1313 and 1349-1356. That a pair of phosphotyrosine residues may be involved has been shown for the PDGF receptor, where Tyr 740 and Tyr 7J ι are known to form the PI 3-kinase binding site (Fantl, W.J., et al.. Cell 69.:413-423 (1992); Kaziauskas, A., et al., Mol. Cell. Biol. 12:2534-2544 (1992)). Association of p85 or PI 3-kinase holoenzyme with HGF/SF receptor Tyr-Phe mutants. A series of constructs were made by site-directed mutagenesis of the wild type receptor cDNA according to standard methods well known to the skilled in the art. These constructs were transiently expressed in COS 7 cells, to obtain the corresponding Tyr-Phe receptor mutants Phe 1003 , Phe 13ff7 , Phe 1313 , Phe 1349 , Phe 1356 , and Phe 1365 . In addition to single amino acid substitutions, some multiple substitutions were also made. In particular, we produced the two double site mutants necessary to further elucidate the results of the competition experiments: the mutant Phe, 3σ 313 and the mutant Phe 1349 ., 356 . Fig. 4 shows the results of an association experiment similar to that represented in Fig. 1, carried out using the same source of p85 (expressing Sf9 cells) , and using lysate of transfected COS 7 cells as a source of wild type and mutant HGF/SF receptors. Transfected COS 7 cells express the single-chain receptor precursor as well as the proteolytically processed mature form in a 1:1 ratio. After the association reaction the samples were split in two and processed differently to yield the results shown in panels A and B. In panel A both the receptor and p85 are visualized by means of a kinase assay. This panel shows that the mutant receptors are all active, and are present in comparable amounts. While all the other mutants (and in particular Phe, 3σ 313 ) still bind and phosphorylate p85, only the double mutant Phe 1349 . 1356 does not. In panel B after the association the kinase assay was omitted, the samples were run in SDS- PAGE and transferred to nitrocellulose. The Western blot was then decorated with monoclonal antibodies specific for p85. This experiment confirms that only the mutant Phe 1349. , 3J6 has lost the ability to bind p85. It should be noted that comparing panels A and B the mutant Phe 13S6 , although still capable of binding p85, seems to be defective in phosphorylating it. This suggests that in the complex with this receptor mutant, p85 may not be positioned correctly for efficient phosphorylation. Fig. 5 shows that similar results can be obtained also in vivo. In this experiment the receptor was immunoprecipitated from lysates of transfected COS 7 cells after HGF/SF stimulation. Lysis and immunoprecipitation were done in the presence of sodium orthovanadate, to prevent receptor de- phosphorylation. A PI 3-kinase assay was then carried out on the receptor immunoprecipitates, equalized for Met protein content, to quantify the amount of endogenous PI 3-kinase co-precipitated in complex with the receptor. Only the Phe 1349. 1356 double mutant co-precipitated with an amount of PI 3- kinase activity lower than thrt associated to the wild type receptor. The residual activity bound to the Phe 1349 . 1356 double mutant is probably due to the formation of receptor dimers with the endogenous Met protein from COS 7 cells. This interpretation is supported by the fact that the same amount of residual binding is also present on immunoprecipitates obtained from COS 7 cells transfected with a kinase-inactive mutant (TK\ Fig. 5) . The results of this second set of experiments indicate that residues Y 1349 and Yι 356 mediate binding of PI 3-kinase to the HGF/SF receptor, while residues Y 1307 and Y 1313 do not. Phosphopeptide mapping of wild type and mutant receptors. The results obtained using the mutant receptors imply that tyrosines 1349 and 1356 are phosphorylated in vivo. A synthetic peptide (I24K) was constructed to correspond to the tryptic peptide including these two residues. This peptide required a combination of aqueous and organic solvents for best recovery and eluted at a very late time from the HPLC column used for the separation (see panel A of Fig. 6) . When the same procedure was used to run a tryptic digest obtained from a wild type receptor that had been phosphorylated in vitro, a peak eluting at a time very close to that of the non-phosphorylated I24K peptide was recovered. (Fig. 6, panel B) . This novel peak is absent in the double- site mutant (Fig. 6, panel C) and is reduced in the single- site mutants (not shown) . All receptors were expressed in COS 7 cells and phosphorylated n vitro prior to tryptic digestion. These results indicate that tyrosines 1349-1356 are indeed in vitro phosphorylation sites and, in combination with the association experiment shown in Fig. 5, strongly suggest that the same tyrosine residues are also in vivo phosphorylation sites. Evaluation of the relative affinities of phosphotyrosine 1349 and 1356 for the N- and C- SH2 domains of p85. The presence of two SH2 domains in the p85 molecule and the need to eliminate two phosphotyrosines in the HGF/SF receptor to abolish PI 3-kinase binding, suggest a model in which each SH2 domain interacts with one of the two tyrosines (Kashishian, A., et al., EMBO J. !! '•1373-1382; Kavanaugh, W.M., et al., Mol. Cell. Biol. 11:3415-3424 (1992)). It is therefore interesting to measure the relative affinities of the two phosphopeptides for the N- and C- terminal SH2 domains of p85. We initially attempted to do this using biospecific interaction analysis with the BIAcore instrument (Jonsson, U. , et al., Biotechniques 11:520-527 (1991); Jonsson, U. , and M. , Malmquist. In F. Turner (ed) , Advances in Biosensors, vol. 2 JAI Press, London (1992); Karlsson, R. , et al., J. Immunol. Meth. 145:229-246 (1991)). However, the coupling of the phosphopeptides to the matrix either directly or, after biotinylation, by binding to matrix-immobilized avidin, resulted in no significant response. This was presumably due to the fact that the phosphotyrosine in these peptides is at the N-terminus and immobilization perturbs its binding capacity. We therefore did the affinity measurements in an indirect way, by measuring the ability of the phosphopeptides to inhibit the interaction of the SH2 domains with an immobilized phosphopeptide which includes phosphotyrosine 751 (Y 751 ) in the human PDGF receptor and has been shown to have a high affinity for the two SH2 domains. The N- and C- SH2 domains of p85 were mixed with a range of concentrations of the Met phosphopeptides and injected over immobilized Y751 phosphopeptide. Fig. 7 shows the results of these measurements, expressed as % inhibition of binding to phosphopeptide Y751. Although it was not possible to derive the absolute affinities for these interactions, comparison of the values at which half-maximal inhibition is observed provided useful information about the relative affinities. A summary of the data is shown in panel C. The highest apparent affinity is displayed by the Y, 313 phosphopeptide, which contains the canonical YXXM motif. The phosphopeptides Y 1349 and Y I356 , which include the unconventional binding site YVXV, also inhibit binding of p85 N- and C- SH2 domains to phosphopeptide Y751, but at higher concentrations. All phosphopeptides, but more evidently Y 1313 , show a higher affinity for the C- SH2 than for the N- SH2. These data are in agreement with those obtained from the experiment shown in Fig. 2 , and indicate that, at least in vitro and under our experimental conditions, the novel binding motif Tyr- Val-Xxx-Val (YVXV) has an affinity for p85 two orders of magnitude lower than the canonical consensus. EXAMPLE 5 Transforming activity of TPR-MET tyr-phe mutants Through the experiments described in Example 4, the tyrosine residues in positions 1349 and 1356 of the HGF/SF receptor (encoded by the MET protooncogene) have been identified as docking sites involved in recruiting and activating PI 3-kinase and possibly additional cytoplasmic transducers. If permanently activated, the transducers act as continuos effectors of the mitogenic signal, thus producing the oncogenic transformation of the cell. In order to demonstrate the importance of the tyrosine residues in position 1349 and 1356 of the HGF/SF receptor in the process leading to oncogenic transformation, we took advantage of the TPR-MET molecule, the permanently activated form of the MET protooncogene (Gonzatti-Haces, et al. Proc. Natl. Acad. Sci. USA 85: 21-25 (1988)). TPR-MET results from a DNA rearrangement between TPR sequences from chromosome 1 and MET sequences from chromosome 7. The TPR-MET product has a constitutive tyrosine kinase activity responsible for transformation of NIH 3T3 fibroblasts. Through site-directed mutagenesis, we have mutated to phenylalanine the tyrosine residue in position 1349 and 1356 of the TPR-MET molecule. The TPR-MET wild type protooncogene as well as the mutated forms TPR-MET-Phe 1349 , TPR-MET-Phe 1356 and TPR-MET-Phe 1349 . 1356 have been used to perform a Focus Formation Assay. In this assay Fisher Rat fibroblasts were transfected by calcium phosphate with the different TPR-MET constructs cloned in the pXMT2 plasmid (Sambrook, et al. Molecular Cloning. A laboratory manual (Second edition) page 16.22, Cold Spring Harbor Laboratory Press (1989)). Cells were grown in DMEM containing 5% Foetal Calf Serum and foci were counted after 10 days. The results are summarized in the following table and illustrated in Fig. 9. As can be appreciated either from the above table or from Figure 8 the mutation of the Tyr 1349 but especially of Tyr 1356 produces a substantial decrease in the number of the transforming foci. Moreover, when both the Tyr residues are mutated to Phenylalanine, the transforming activity of TPR-MET is completely abolished. These data provide a further demonstration of the biological importance of these sites in that intracellular transduction of the mitogenic signal. The phosphopeptides of the invention which are able to prevent the binding of the intracellular transducers to τ Y r i3 and τ Y r ι 3 56 of the HGF/SF receptor are therefore potential inhibitors of the oncogenic transformation. EXAMPLE 6 MATERIALS AND METHODS Cell lines. Lung carcinoma A549 cells and COS-1 cells were routinely cultured in RPMI medium supplemented with 10% FCS. The PA317 amphotropic virus packaging cell line (Miller and Buttimore (1986) Mol. Cell. Biol. 6 : 2895-2902) and the ecotropic virus packaging cell line Psi-2 (Mann et al (1983) Cell 3.3: 153-159) were maintained in Dulbecco's modified Eagle's medium supplemented with 10% FCS. Monoclonal antibodies and polyclonal antisera. Anti-She polyclonal antisera were produced by immunizing rabbits with She SH2 domain expressed in bacteria. Anti-TAG serum was produced against a PML peptide (Pandolfi et al. , Oncogene 6.: 1285-1292 (1991)) . Monoclonal antibodies to phosphotyrosine were purchased from Upstate Biotechnology. Anti-Met antibodies were raised against a synthetic peptide corresponding to the 19 C-terminal aminoacids of the human Met protein (Data Bank reference no. X54559) . Immunoprecipitation and western blotting procedures. Lysates were prepared from serum starved and SF/HGF treated A549 cells. Cells were lysed on ice in PY buffer (20mM Tris HCl pH 7.8, 50 mM NaCl, 50mM NaF, 30mM Na 4 P 2 0 7 , 5mM EGTA, ImM sodium orthovanadate, 1% vol/vol Triton X-100) containing freshly added protease inhibitors (ImM phenyl ethyl sulphonyl fluoride, 10 mg/ml leupeptin and 5mg/ml aprotinin) . Lysates were clarified by centrifugation at 4°C and protein concentration determined by BCA reagent (Pierce) . For immunoprecipitation experiments, appropriate antibodies were adsorbed on Protein A Sepharose (Pharmacia) and then incubated with cell lysates for 1.5 hrs. at 4°C. Immune complexes were washed 3 times with ice cold NET buffer (50mM Tris HCl pH 7.5, 150mM NaCl, 0.1% NP-40, ImM EDTA pH 8.0, 0.25% gelatin), eluted and denatured by heating for 3 min. at 95°C in reducing Laemmli buffer; proteins were then resolved on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) . For im unoblot analysis, either specific immunoprecipitates or 20-50 mg total cell lysates were transferred onto nitrocellulose filters after SDS-PAGE. After blocking nonspecific reactivity with 2% nonfat dry milk dissolved in TBST (20mM Tris-HCl pH 7.8, 150 mM NaCl 0.02% Tween 20) (1 hr incubation at 22°C) , filters were probed for 2 hrs at 22°C with specific antibodies diluted in TBST. After extensive washing, immune complexes were detected with horseradish-peroxidase conjugated species-specific secondary antiserum (Bio Rad) followed by the enhanced chemiluminescence reaction (ECL™, Amersham) . cDNA site-directed mutagenesis and expression. The cloning of the MET cDNA has been reported previously (Ponzetto et ai. , Oncogene 6 : 553-559 (1991)), EMBL Data-Bank reference no. X54559) . The 3' end fragment from nucleotide 2355 to the end was subcloned in pSELECT™-l. Site-directed mutagenesis was performed using an in vitro oligonucleotide site-directed mutagenesis system (Altered Sites™ in vitro Mutagenesis System, Promega) . Oligonucleotides were synthesized using an Applied Biosystem 391 apparatus. Mutant clones were identified by sequencing (T7 sequencing kit from Pharmacia) . Full size MET cDNAs carrying the appropriate Tyr→Phe mutation were reconstructed in the PMT2 vector which contains the major late Adenovirus promoter. All plasmids were transfected by lipofeetin (GIBCO BRL) in COS 1 cells. The She cDNA carrying the mutation Y 317 →F was cloned into the mammalian expression vector LXSN. The mutated cDNA was tagged with a foreign epitope by in-frame fusion with a 162 bp fragment of the PML cDNA (Pandolfi et al. , ibid) . The tagged cDNA encodes PML-tagged She proteins of 53 and 58 kDa as a result of alternative initiation usage. Detailed description of this construct will be reported elsewhere (Salcini et al. , in preparation) . The expression vector was cotransfected with a neomycin resistance gene in A549 cells by calcium phosphate. Stable cell lines expressing the tagged She proteins were selected by G418. In vitro binding studies using GST-fusion protein. The region of the Grb2 cDNA corresponding to its SH2 domain (from nucleotide position 256 to nucleotide position 551) was isolated using polymerase chain reaction (PCR) and cloned into the BamHI-EcoRI sites of the bacterial expression plasmid pGEX-2T (GST-Grb2) . Cultures of bacteria expressing GST, GST-Grb2 or GST-She (Segatto et i. , Oncogene 2105-2112 (1993)) were grown for 3-4 hours at 37°C in LB medium containing ImM IPTG. Bacteria were centrifuged, resuspended in 1/100 volume of ice-cold PY buffer, without Triton™ and lysed by sonication. After adding Triton X- 100 to 1%, lysates were clarified by centrifugation. Recombinant proteins were purified onto glutathione Sepharose™ (Pharmacia) and used as such for binding assays. For each reaction, about 5 μg of GST, GST-Grb2 or GST-She bound to glutathione Seharose was incubated for 2 hrs. at 4°C with 300 mg of appropriate cell lysate made in PY buffer. Protein complexes were washed 5 times in ice cold PY buffer, eluted and denatured by heating at 95°C for 3 min in Laemmli buffer, resolved on SDS-PAGE and analyzed by im unoblot. Overexpression of She proteins. The LSHCSN plasmid was constructed by cloning the She coding sequence (Pelicci et a Cell 2(D: 93-104 (1992)) in the EcoRI restriction site of the LXSN retrovirus plasmid (Miller et al. , (1989); gifted from D. Miller) . LXSN or LSHCSN plasmids were transfected into the Y2 of PA317 retrovirus packaging cell lines by the calcium phosphate precipitation procedure (Sambrook et al. Molecular Cloning: A Laboratory Manual, 2nd Ed., Cold Spring Harbor Laboratory, Cold Spring Harbour, NY (1989)). After 48 hours, the Y-2 supernatants were used to infect PA317. The cells were then selected with G418 containing medium under limiting dilution conditions. One virus-producing clone was selected, based on high levels of exogenous She expression and viral titer and used to infect target cells. BIAcore analysis. The basic principles of operation as well as the methodology for obtaining kinetic measurements of SH2 domain interactions using the BIAcore instrument (Pharmacia) have been previously described in detail (Panayotou et al. , Mol. Cell. Biol. 13.: 3567-3576 (1993), Ponzetto et al.. Mol. Cell. Biol. 13 . : 4600-4608 (1993)). Purified GST-SH2 domains or intact proteins were desalted in BIAcore running buffer (20mM Hepes, pH 7.4, 150 mM NaCl, 3.4 mM EDTA, 0.005% Tween 20 and 4mM DTT) and injected over avidin- immobilized, biotinylated phosphopeptides. The amount of phosphopeptides immobilized was normalized by measuring the binding of anti-phosphotyrosine antibodies. Association was measured over a range of protein concentrations and dissociation of bound material was allowed to occur either in buffer flow or upon injection of 20μM competing, non-biotinylated phosphopetide. Peptide and protein concentrations were calculated by amino acid analysis on an Applied Biosystem amino acid analyzer. Assay for cell growth and motility. 2.5xl0 3 cells were plated in 96-well plates (Costar) in DMEM medium containing 10% FCS (Flow) . After 24 hours the medium was removed and replaced with DMEM containing 5% FCS with a wide range of SF/HGF concentrations (1- 10 ng/ml) . Cell number was estimated after staining with crystal violet by a colorimetric assay (Kueng et ai. , Anal. Biochem. 182: 16-19 (1989)); the wells were read at 595 nm in a Microplate Reader (Model 3550, Bio-Rad) . Blind-well boyden chambers and polyvinylpyrrolidone-free polycarbonate filters (13 mm 8μm pores) used for chemotaxis studies were purchased from Nucleopore. Chemotaxis assays were performed as previously described (Albini et al.. Cancer Research 42: 3239-3245 (1987)). Cells were labelled with 5-[ I25 I]iodo-2'-deoxyuridine (3 μCi/ml In RPMI 1640 medium plus 10% FCS) . After 16-20 hr of incubation, cells were trypsinized and washed three times with FCS free medium. 3xl0 5 cells resuspended in the FCS free medium were plated in the upper part of Boyden chambers; in the lower chambers, FCS free medium with or without SF/HGF (5-40 U/ml) was added. Boyden chambers were incubated for 6 hr at 37°C in a 5% C0 2 -water saturated atmosphere. Cells attached to the upper side of the filters were mechanically removed after incubation, while the filters with cells migrated to the lower side were fixed and counted in a y- counter. RESULTS She proteins bind the tyrosine phosphorylated SF/HGF receptor via the SH2 domain. Lung carcinoma A549 cells express functional SF/HGF receptors and the three She isoforms of 46, 52 and 66 kDa. To test if the tyrosine phosphorylated SF/HGF receptor and She form a stable complex in vivo, lysates form SF/HGF-treated cells were immunoprecipitated with anti-Met and im unoblotted with anti-She antibodies. She proteins co-precipitated with the SF/HGF receptor (Fig. 1A) . Similar results were obtained in mirror experiments, where anti-She immunoprecipitates from lysates of SF/HGF-treated A549 cells were probed with anti-receptor (anti- Met) antibodies. She proteins co-precipitated with the SF/HGF receptor (Fig. IB) . These results demonstrate that SF/HGF receptor and She are associated in SF/HGF-stimulated cells. To further prove that the association between SF/HGF receptor and She is strictly dependent on receptor tyrosine phosphorylation, similar experiments were performed using COS-1 cells lysates transiently expressing the cDNAs of either wild- type SF/HGF receptor or of a kinase-defective receptor mutant (Lys 1110 →A) . As previously described (Longati et al, in press) , the wild-type receptor overexpressed in COS-1 cells is constitutively phosphorylated in vivo, while the kinase-inactive Lys 11I0 →A mutant is not phosphorylated (Fig. 2 A and B) . Stable complexes between the transfected receptor and the endogenous She occurred only in COS-1 cells expressing wild-type tyrosine- phosphorylated receptors (Fig. 2C) . The Shc-SF/HGF receptor interaction was also explored by reconstituting the complex in vitro using the She SH2 domain, expressed in bacteria as a GST- fusion protein. The immobilized Shc-SH2 domain formed a stable association with the tyrosine-phosphorylated receptor solubilized from SF/HGF treated A549 cells, but not with the unphosphorylated receptor solubilized from control cells (Fig. 3A) . Binding assays carried out with control GST protein were negative. These results indicate that the SH2 domain of She is sufficient for binding to the autophosphorylated SF/HGF receptor in vitro. She proteins bind to phosphotyrosines Y 139 and Y 1356 of the SF/HGF receptor tail. By phosphopeptide mapping of wild-type and mutant SF/HGF receptor, it has been shown that two residues located in the C- terminal tail of the receptor (γ 139 and γ 1356 ) are phosphorylated in response to ligand binding (Ponzetto et ai. , 1993 (ibid)). The possible involvement of these sites in mediating the interaction with She was studied by association experiments with receptor mutants where either one or both these tyrosines were mutated to phenylalanine (Y 1349 →F, γ 1356 →F or Y 139 ' 1356 →F) . As previously shown, receptor molecules carrying individual or combined mutations at these sites are endowed with native tyrosine kinase activity (Ponzetto et ai. , 1993 (ibid)). COS-1 cells were transfected with constructs expressing the receptor mutants and immunoprecipitated with anti She antibodies; immunoprecipitates were blotted with anti-Met receptor antibodies. The ability of the single mutant receptors Y ,39 →F or the γ I356 →F to associate with endogenous She was only slightly lower than that of the wild type receptor or that of a control receptor carrying an irrelevant (Y ,003 →F) mutation. Conversely, the γ^^^ →F ouble mu tant completely lost its ability to bind She proteins (Fig. 4) . The direct interaction between the SH2 domain of She and phosphotyrosine Y 1349 or Y 1356 was confirmed by real-time Biosensor analysis (Panayotou et al. , ibid; Felder et al. , Mol. Cell. Biol. 13: 1449-1455 (1993)). The synthetic phosphopetide VNATY ,356* VNVK, derived from the receptor tail sequence, was specifically bound by the affinity-purified GST-SH2 domain of She (Fig. 5) . Similar results were obtained with the peptide IGEHY 1349* VHVN. In both cases, the affinity constant, calculated from the ratio between the dissociation rate (K di „) and the association rate constants ( κ «8» ) i was to ° high to be exactly determined. These data show that She binds with low affinity to either tyrosine 1349 or tyrosine 1356 of the SF/HGF receptor tail. Overexpression of She proteins increases the motogenie response to SF/HGF. SF/HGF is motogenie for epithelial cells that, after stimulation, migrate through the filters of blind-well Boyden chambers (Giordano et al.. Proc. Natl. Acad. Sci. USA 90: 649-653 (1993)). The effect of She on the motogenie response was investigated by overexpressing the protein in A549 cells. Cells were infected with an amphotropic retrovirus carrying the She cDNA and a number of different infected bulk cell populations were chosen for their high levels of She expression, according to western blot analysis with anti-She antibodies. The motogenie response of A549 cells overexpressing She proteins was significantly higher than that elicited in control uninfected cells or in cells infected with the vector alone (Fig. 6, lower panel) . Higher responses to SF/HGF by cells overexpressing She were observed at all ligand concentrations tested (Fig. 6, upper panel) . The mitogenic response was measured either by cell count or by thymidine incorporation. She overexpression in A549 cells had no effect on cell growth in response either to SF/HGF or to serum. Similarly, the SF/HGF-induced guanine nucleotide exchanger activity on Ras, measured as previously described (Graziani et al.. J. Biol. Chem. 268: 9165-9168 (1993)), was not significantly affected by overexpression of exogenous She. She proteins are phosphorylated on Y 317 after binding to the SF/HGF receptor. To determine if She is phosphorylated in response to the activation of SF/HGF receptor kinase A549 cells were stimulated with recombinant SF/HGF, lysed, immunopreeipitated with anti-She and immunoblotted with anti-phosphotyrosine antibodies. A marked increase in tyrosine-phosphorylation of p46 shc , p52 Shc and p66 Shc was detectable in A549 cells after 5 min. stimulation (Fig 1C) , indicating that She is a substrate of the SF/HGF receptor. Similar experiments were performed in COS-1 cells transfected with the SF/HGF receptor. In cells overexpressing the wild-type (constitutively active) receptor kinase, endogenous She proteins were tyrosine phosphorylated. However, She was not phosphorylated in COS-1 cells transfected with the Lys 1110 →A kinase negative receptor (Fig.2D). By phosphopeptide mapping and mutation analysis it has been shown that the major phosphorylation site of She in EGF-treated cells is Y 317 (Salcini et a_l. , in preparation) . To ascertain that the same residue is also phosphorylated after SF/HGF treatment, a tagged SHC cDNA with a Y 317 →F mutation was expressed into A549 cells. In these cells, after SF/HGF treatment, the Y 317 →F mutant, selectively immunopreeipitated by anti- "tag" antibodies was not phosphorylated on tyrosine (Fig. ID) . She proteins phosphorylated on Y 317 form specific complexes with the Grb2 "adaptor". The possibility that SF/HGF triggers formation of a Shc-Grb2 complex in A549 cells following SF/HGF stimulation was tested by probing Western blots of anti-She immunoprecipitates with anti- Grb2 antibodies. As shown in Fig. IE, the She protein phosphorylated in response to SF/HGF is associated with Grb2. This association is mediated via the SH2 domain of Grb2, as shown by in vitro experiments using immobilized SH2 domain of Grb2 (expressed in bacteria as GST fusion protein) and cytoplasmic lysates prepared from control or SF/HGF-stimulated A549 cells. The amount of She bound by the Grb2 fusion protein increases significantly after SF/HGF stimulation (Fig.3B). Kinetic parameters and equilibrium dissociation constants or this interaction were derived using a biosensor to measure in real¬ time binding of the Grb2 GST-SH2 fusion protein with the immobilized tyrosine-phosphorylated She peptide DDPSY 317* VNVQ (Fig. 7). The data obtained were used to calculate the K ass (2.6 x 10 5 M^s" 1 ) as shown in Fig. 7C. The K dilιs was measured both in buffer and in the presence of competing phosphopeptide to prevent re- binding. As shown in Fig. 7B, addition of the competing phosphopeptide had a dramatic effect on dissociation rate, as previously observed for other SH2 domain-phosphopeptide interactions (Panayotou et al. , 1993 (ibid); Felder et aJL. , 1993 (ibid)). The value of the K diss obtained was 0.04 S "1 , giving an overall affinity of 153 nM. These data show that phosphorylation of She proteins on tyrosine Y 317 in response to SF/HGF determine the formation of high affinity docking site for the Grb2 "adaptor". Phosphorylated She proteins may thus function as bridging molecules between the activated SF/HGF receptor and Grb2. Interestingly, the amino acid sequence of the She docking site for Grb2, Y 317 VNV, is identical to the sequence located in the SF/HGF receptor tail (Fig 8) , Y 1356 VNV, is identical to the sequence located in the SF/HGF receptor tail (Fig 8), Y ,356 VNV, which has been shown to directly bind Grb2 upon ligand stimulation (Ponzetto et ai. , submitted) . The She proteins do not form concatamers The She sequence Y 317 VNV is identical to one of the two She binding sites present in the SF/HGF receptor (Fig.8). This observation suggests that She may form concatamers by binding phosphotyrosine Y 317 of another She molecule. The biosensor was used to compare binding of the She SH2 domain to the phosphopeptide DDPSY 317 VNVQ. present on the She molecule, and to the phosphopeptide VNATY 13S6 VNVK. present on the SF/HGF receptor. Shc-SH2 bound much more weakly to the She-derived phosphopeptide than to the SF/HGF receptor-derived phosphopeptide (Fig.5). These data indicate that amino acids at the N-terminal of Y 317 (in She) and of Y 1356 (in SF/HGF receptor) are recognized by the SH2 domain of She. Thus She-She association is not favoured in vivo, and the She phosphotyrosine residue Y 317 is available to bind other molecules, rather than to mediate the formation of concatamers. CONCLUSIONS In conclusion, a peptide having a length of e.g. 4 to 20 amino acids encompassing the docking site of She (Y 317 VNV) , particularly thepeptideH-Asp-Asp-Pro-Ser-Tyr * -Val-Asn-Val-Gln-OH (DDPSY * VNVQ) and a peptide having a length of e.g. 4 to 20 amino acids encompassing the Tyr 1356 recognition motif of the hepatocyte growth factor receptor (Y 1356 VNV) , particularly the peptide H-Val-Asn-Ala- Thr-Tyr * -Val-Asn-Val-Lys-OH (VNATY * VNVK) , wherein Tyr * (Y * ) represents a phosphorylated or unphosphorylated tyrosine residue, are able to bind Grb2-SH2 domain. Thus, they are useful to compete for and to prevent the SH2 association of Grb2 protein with tyrosine phosphorylated receptors such as activated hepatocyte growth factor receptor (HGF/SF receptor) , PDGF receptor, EGF receptor or with other cytosolic tyrosine phosphorylated transducers such as She or IRS-1 protein, preventing mitogenesis and hence tumoral proliferation. On the other hand, peptides encompassing the Tyr 1356 or the Tyr 1349 recognition motif of the hepatocyte growth factor receptor (Y- i - W VNv or Y 1349 VHV respectively) , particularly the above mentioned peptide H-Val-Asn-Thr-Tyr * -Val-Asn-Val-Lys-OH (VNATY * VNVK) and the peptideH-Ile-Gly-Glu-His-Tyr * -Val-His-Val-Asn-OH (IGEHYNHVN) , or a peptide containing both the above mentioned tyrosine residues such as H-Ile-Gly-Glu-His-Tyr * -Val-His-Val-Asn-Ala-Thr-Tyr * -Val- Asn-Val-Lys-OH (IGEHY * VHVNATY * VNVK) wherein Tyr * (Y * ) represents phosphorylated or unphosphorylated tyrosine residue, are able to bind Shc-SH2 domain. Thus, they are useful to compete for and to prevent the SH2 association of She protein with tyrosine phosphorylated receptors such as activated hepatocyte growth factor receptor, EGF receptors or with other cytosolic tyrosine phosphorylated transducers like IRS-1 or cytosolic tyrosine kinases such as Src, preventing mitogenesis and particularly motogenesis and hence preventing spreading of tumour cells. Thus, the peptides exert antitumoral and antimetastatic actions. As mentioned above, the peptide of the invention may be advantageous!. / administered in unphosphorylated form as a pro- drug; in this case the peptide may be biochemically transformed into its phosphorylated form inside the cell where it exerts its pharmacological action.

Claims: CLAIMS 1. A peptide having the sequence of a portion of the intracellular region of the human hepatocyte growth factor receptor, which peptide can bind to a cytosolic signal transducer. 2. A peptide according to claim 1 which can inhibit binding between p85 subunit of phosphatidyl inositol 3- kinase and the activated hepatocyte growth factor receptor. 3. A peptide according to claim 1 which can inhibit binding between She protein and the activated hepatocyte growth factor receptor. 4. A peptide according to claim 1 which can inhibit binding between She protein and a cytosolic signal transducer. 5. A peptide having the sequence of a portion of She protein, which peptide can bind to a cytosolic signal transducer. 6. A peptide according to claim 5 which can inhibit binding between She protein and Grb2 protein. 7. A peptide according to claim 5 which can inhibit binding between Grb2 protein and the activated hepatocyte growth factor receptor. 8. A peptide according to any one of the preceding claims having the sequence X N -YVN(or H)V-X C wherein X N and X c are each sequences of from 0 to 16 amino acids. 9. A peptide according to claim 8 wherein X N and X c are sequences which flank one of the YVN(or H)V sequences in the HGF/SF receptor and She protein. 10. A peptide according to claim 9 which is H-Asp-Asp- Pro-Ser-Tyr*-Val-Asn-Val-Gln-OH wherein Tyr* is a phosphorylated or unphosphorylated tyrosine residue. 11. A peptide according to claim 9 which is H-Val-Asn- Ala-Thr-Tyr*-Val-Asn-Val-Lys-OH wherein Tyr* is a phosphorylated or unphosphorylated tyrosine residue. 12. A peptide according to claim 9 which is H-Ile-Gly- Glu-His-Tyr*-Val-His-Val-Asn-OH wherein Tyr* is a phosphorylated or unphosphorylated tyrosine residue. 13. A peptide according to claim 9 which is H-Ile-Gly- Glu-His-Tyr*-Val-His-Val-Asn-Ala-Thr-Tyr*-Val-Asn- Val-Lys-OH wherein Tyr* is a phosphorylated or unphosphorylated tyrosine residue. 14. A peptide according to claim 9 which is H-Tyr*- Val-His-Val-Asn-Ala-Thr-Tyr-OH wherein Tyr* is a phosphorylated or unphosphorylated tyrosine residue. 15. A peptide according to claim 9 which is H-Tyr*- Val-His-Val-Asn-Ala-Thr-Tyr*-Val-Asn-Val-Lys-OH wherein Tyr* is a phosphorylated or unphosphorylated tyrosine residue. 16. A peptide according to claim 9 which is H-Tyr*- Val-Asn-Val-Lys-Cys-Val-Ala-OH wherein Tyr* is a phosphorylated or unphosphorylated tyrosine residue. 17. A peptide according to claim 1 which is: H-Tyr*-Asp-Ala-Arg-Val-His-Thr-Pro-OH H-Tyr*-Arg-Ala-Thr-Phe-Pro-Glu-Asp-OH H-Tyr*-Pro-Leu-Thr-Asp-Met-Ser-Pro-OH H-Tyr*-His-Gly-Thr-Leu-Leu-Asp-Asn-OH H-Tyr*-Het-Lys-His-Gly-Asp-Leu-Arg-OH H-Tyr*-Leu-Ala-Ser-Lys-Lys-Phe-Val-OH H-Tyr*-Asp-Lys-Glu-Tyr-Tyr-Ser-Val-OH H-Tyr*-Tyr-Ser-Val -His-Asn-Lys-Thr-OH H-Tyr*-Ser-Vgl-His-Asn-Lys-Thr-Gly-OH H-Tyr*-Pro-Asp-Val -Asn-Thr-Phe-Asp-OH H-Tyr*-Leu-Leu-Gln-Gly-Arg-Arg-Leu-OH H- Tyr* -Cys-Pro- Asp-Pro- Leu- Tyr-Glu-OH H-Tyr*-Glu-Val -Met-Leu-Lys-Cys-Trp-OH H-Tyr*-Pro-Ser-Leu-Leu-Ser-Ser-Glu-OH wherein Tyr* is a phosphorylated or unphosphorylated tyrosine residue. 18. A process for preparing a peptide as claimed in any one of the preceding claims, which process comprises chemically sinthesizing the peptide from single amino acids and/or preformed peptides of two or more amino acid residues. SUBSTITUTESHEET(RULE25) 19. A process according to claim 18 wherein a prephosphorylated protected tyrosine residue is directly introduced during a solid phase synthesis. 20. A process according to claim 18 wherein a tyrosine residue of a protected preformed peptide is phosphorylated while the peptide is attached to a solid support. 21. A pharmaceutical composition comprising a physiologically acceptable carrier or diluent and, as active ingredient, a peptide as claimed in any one of claims 1 to 17. 22. A peptide according to any one of claims 1 to 17 for use in treatment of the human or animal body by therapy. 23. A peptide according to claim 22 for use in treatment of a neoplastic disease. 24. Use of a peptide as claimed in any one of claims 1 to 17 in the manufacture of a medicament for treatment of a neoplastic disease.

Inventors: COMOGLIO PAOLO, PONZETTO CAROLA, COMOGLIO, PAOLO, PONZETTO, CAROLA
Applicants: ERBA CARLO SPA, FARMITALIA CARLO ERBA S.R.L.
Application year: 1994
Main classification: C07K14
IPC codes: A61K38, A61P35, C07K7, C07K14, C12N9, C12N15, C12P21, C12R1